On Mothering Sunday, actress Phyllida Law talks about the close bond with her
daughters Sophie and Emma Thompson

Phyllida Law is worried about her daughter, Emma Thompson. “She’s in New York singing Sweeney Todd with the New York Philharmonic,” she says, in her soft Scottish accent. “And she’s flying back today, just for the night, to see Gaia [Thompson’s 13-year-old daughter] in her school’s production of West Side Story. I’m so anxious about her.”

What can possibly trouble Law? Thompson, 54, is surely the most capable woman on the planet? Does she fret about her flying? “No, but she has a cold!” Law exclaims. “And she’s singing with bloody Bryn Terfel; what a pressure is that? It’s like you’re doing it yourself – not that I have ever done anything like that, but I would have agonised. I won’t be well until it’s all over.”

Such are the trials of motherhood, a subject in which Law, 81, is extremely well versed. Her daughters, Emma and Sophie, 52, are mothers. She also nursed her own mother, Meg, who had Alzheimer’s, and her mother-in-law lived with the family for the last 17 years of her life.

Law’s affecting accounts of caring for both women were originally published separately. They have now been compiled into one book – Three Mothers (And a camel) – which includes new chapters from Law and her daughters.

“Long ago, I remember thinking I could never be as good, kind, wise, loving and generally brilliant and gorgeous as her,” writes Emma. “It’s taken me over half a century to stop trying.”

Law, however, disagrees. “My daughters are much better mothers than I was,” she says. “They just manage everything better. They take it all very seriously.”

Law speaks non-stop in vague and, at times, surreal sentences, so that you can see why she became the model for Ermintrude in The Magic Roundabout, her late husband Eric’s creation.

We’re sitting in front of the fire in Law’s Aladdin’s cave of a garden flat in a salubrious, but unflashy, street in West Hampstead. The walls are covered in oil paintings, the shelves groaning with family photos and trinkets. Across the road live Emma and her family – her second husband, the actor Greg Wise (the first was Kenneth Branagh), Gaia, and their adopted Rwandan son, Tindy, 26, a former child soldier.

Sophie used to live on the street, too, but a few years ago she moved a couple of miles away with her husband, the sitcom writer Richard Lumsden, and sons Ernie, 17, and Walter, 14. “Having boys in the family at last was terribly exciting,” says Law. “Before they were born, we’d never seen that appurtenance. Emma and I went thundering up the hill to have a look.”

Mothering Sunday was marked when Law’s daughters were younger. “When they were gels, they used to come in with the odd bunch of daffodils, and the Brownies made them do things.”

Indeed, the family is united to a fault, eating together almost every night. “I generally get a phone call at about six and all that has to be said is, 'The bar is open’, and I go across the road for dinner.”

Their proximity is just as well: when her daughters first left home – for Cambridge and the Bristol Old Vic Theatre School respectively – Law was devastated. “You feel as though the ground’s been whipped from under your feet and you’re … I’m not going to say what I was going to say because it’s a four-letter word.”

Law is startlingly beautiful, with glowing skin and smoke-grey hair piled on top of her head, elegant bone structure and those blue eyes that Emma has inherited. She radiates gentle amusement, but life’s not been easy. Her journalist father became the leader of an RAF squadron unit during the war and never returned. “I think he believed in free love,” she says. She was evacuated from her native Glasgow, aged nine, and at 13 was sent to boarding school in Bristol.

“I wasn’t unhappy – when you’re a child, you accept things – but I didn’t have a mum all that time, and to be a mum you need examples. Mothering isn’t instinctively learnt. I mean, birds teach each other to sing. Any conversations about yourself, your life, sex – anything like that – was non-existent. I learnt about sex from reading an encyclopaedia.”

In contrast, Emma learnt the facts of life, aged eight, by asking Alec Guinness. “Oh, that was mortifying, though he gave her a very calm and accurate response. My grandson, Walter, showed his teacher a picture of a lighthouse recently and she took it for something else and got very cross. I thought she’d missed the point, really – to have yelled with laughter would have been much the best response.”

Law was 25 when Emma was born. “I was far too young, though, on the other hand, my daughters were ancient when they became mums.” She chuckles. “Emma was 42, or something like that [she was 40 and had IVF].” Eric Thompson wasn’t present at the birth. “I think it’s an outrageous idea. I didn’t want him looking at me like that. He was in the other room watching telly. My sons-in-law were all in the room when their children were born, you couldn’t have stopped them, but men are so much better now about helping in the house.”

The girls attended local state schools, leaving Law in a tizz as to how to care for “day girls”. “I didn’t know the form, so I took it very seriously. I used to make bread the night before to let it rise so it would be ready in time for tea the next day. I’d leave every light on in the house, so it would be welcoming for them coming home. It did used to look like a galleon sailing, with those bow windows. Disgracefully extravagant – I’m sorry, I ruined the whole climate.”

She always attended school performances. “I have vivid memories of Emma in the chorus line with a tutu on, a large person telling everyone where to stand. She looked like the Queen Mother.”

Law always worked as an actor. “But most of the time I was unemployed, so I was at home a lot. I missed Christmas once when the girls must have been about seven and nine. I was in the US doing a play. I wouldn’t have dreamt of coming home; 'the show must go on’ is tattooed on me. They had Dad and Gran, so they were fine, but it nearly killed me.”

The girls got on well, she insists, with no rivalry – despite Emma’s more stellar career. “That used to worry me and obviously we’ve talked about it, but I’ve never had a very interesting career myself so I suppose Sophie relates to me. It’s also true that she may have had a happier life than Emma because of it.”

As children, they were rarely in trouble, bar Emma being caught stealing sweeties. “She must have been about 12. The sweetshop lady told me it was my fault for not giving them enough pocket money.”

Her daughters’ boyfriends were a source of pain. “That was terrible! Agony,” she laughs. “Just as you think they’ve got the perfect boyfriend, that’s it, he’s gone. Emma was in hopeless love once [presumably with Branagh], she drank a whole bottle of sherry and took a flight to New York.”

Throughout the girls’ teenage years, Law was also caring for her mother-in-law, who was growing deaf, and regularly visiting her own mother in Scotland, who died, aged 93, in 1994. Her account of Meg’s decline makes light of the Alzheimer’s, with plenty of droll anecdotes about her trying to make tea in the toaster at 3am. There are brief mentions of tears and sleepless nights, too, hinting at how tough things really were. “I didn’t want to show the sadness; I thought that would be a bit rude.”

Law, a widow since 1982, now frets about how her children will cope with her ageing. “They already don’t allow me to help them any more – elderly ladies wandering around with dusters are very irritating. But I hate to be helped. If people say: 'Shall I take you across the road?’ I’m stupefied. But I must get better, because there are signs I’m dropping off already.”

In the meantime, Law is still acting, and has especially enjoyed working with her daughters, next to Sophie in the film of Emma and with Emma in Nanny McPhee. “It’s incredibly nice, for me anyway. We know about nerves, when to talk, when to shut up.”

In Three Mothers, Emma writes that the only time her mother has “evinced pride” in her daughter was on learning of her degree result (a 2:1). “She screeched for joy and I felt 10 miles high.” Law says her Presbyterian upbringing makes her unable to praise her daughters or revel in their accomplishments.

“If someone says: 'Oh, aren’t you proud of your daughters?’, it’s generally after a performance and has nothing to do with me, so pride just seems self-regarding. But, of course, some brain shift occurs, some easement around the heart, when they tackle life with grace, which they do. That’s all a mother can hope for from her children.”

'Three Mothers (and a camel)’ by Phyllida Law is available to order from Telegraph Books at £11.99 plus £1.35p&p. Call 0844 871 1514 or visit books.telegraph.co.uk